Electromagnetically displacing a shaft in stepwise increments



R. MARlANl 3,530,346 ELECTROMAGNETICALLY DISPLACING A SHAFT IN STEPWISE INCREMENTS Sept. 22, 1970 Filed July 17, 1969 llllllllll- ATTORNEYS U.S. Cl. 318--123 Claims ABSTRACT OF THE DISCLOSURE A toothed wheel is secured to the shaft of a potentiometer and pawl members are positioned adjacent the wheel on opposite sides of the longitudinal axis of the potentiometer shaft. A solenoid is coupled to each of the pa-wls. When the solenoids are individually energized, the pawl coupled thereto will angularly advance the wheel one tooth at a time. The position of the pawls permit stepwise rotation of the potentiometer shaft in opposite angular directions.

The apparatus is provided with an elastomeric resilient member permitting the armature to bounce and co-acts with a combination torsion and compression spring. An electrical circuit with a diode means reduces the power and together with the resilient member contributes to the self-pulsing action of the apparatus.

This invention is a continuation-in-part application of copending application, Ser. No. 632,264 filed Apr. 20, 1967, now abandoned.

This invention relates generally to indexing means for a potentiometer and more particularly to solenoid operated means that permit the potentiometer shaft to be angularly indexed in equal and opposite increments.

There are many instances where it is necessary to control the current flow of a circuit and this is frequently done by otentiometers or rheostats. For certain applications, manual control of the potentiometer shaft may be sufiicient while in other somewhat more critical applications it may be necessary to angularly step the potentiometer shaft by fixed and known increments. Still other installations require a combination of manual and remote control means for the potentiometer. The present invention provides simple, low-cost means for either manually or remotely establishing the angular position of a potentiometer shaft. Where the remote mode is used, the shaft may be angularly displaced in either of two opposite directions in uniform increments. Resilient means are included within each solenoid, intermediate the armature and core piece thereof, to permit the armature to bounce. In addition a diode is included in the circuitry to provide power reduction means.

Accordingly, it is an object of this invention to provide low cost means for angularly displacing a potentiometer shaft in fixed increments.-

It is another object of this invention to provide a single ratchet member coupled to the potentiometer shaft, the ratchet member beingangularly displaced by solenoid means spaced on either side of the potentiometer shaft.

Still another object is to provide resilient internal biasing means for the solenoid armature.

A further object is to include power reduction means within the circuitry of the apparatus.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a pictorial view of the present invention;

nited States Patent Office 3,530,345 Patented Sept. 22, 1970 FIG. 2 is a plan view, partially broken away, of FIG. 1;

FIG. 3 is a side elevation view of the apparatus;

FIG. 4 is a front elevational view, partially broken away and partially in section of the present invention shown in combination with a potentiometer;

FIG. 5 is a detail view of the ratchet and pawl relationship; and

FIG. 6 is a circuit drawing.

Referring now to the drawing, a potentiometer 10 is mounted on a chassis 12 such that shaft 14 extends outwardly from the support wall 16 and the housing 18 of the potentiometer is disposed on the opposite side of the wall. A manually adjustable knob is normally secured to shaft portion 14. Although not specifically illustrated, it should be understood that the potentiometer housing includes a conventional resistance track, wiper and collector means as well as internal stops that limit the angular movement of the shaft. All of these elements are well known in the potentiometer art and need not be discussed in great detail. An extension 20 of the potentiometer shaft extends outwardly of the housing and supports a ratchet wheel 22 having a plurality of teeth 23 integral with the periphery thereof. The ratchet wheel may be press fit or otherwise suitably secured to the shaft so that it rotates together therewith.

Solenoids 30 are mounted on the bottom leg of the chassis 12 and are positioned on either side of the longitudinal axis of the potentiometer shaft. It will be seen in the broken away portion of FIG. 4 that the solenoids include a support bobbin 32 of insulating material and a coil of wire 34 wound around the bobbin. The coil is adapted to be connected to a suitable source of current not shown. Completing the solenoid structure is an axially movable armature 36 that is mounted within the central bore 38 of each bobbin.

Each armature carries its own pawl member 40 at the upper end thereof and a washer 42. As shown particularly in FIG. 5, the free end of each pawl includes an edge 44 that is normally positioned in proximity to but not in engagement with the ratchet teeth 23. When one solenoid is energized, the armature 36 will be pulled downwardly and edge 44 will engage a tooth 23. The linearly downward movement of edge 44 will angularly displace that tooth. It will be appreciated that if the other solenoid is energized instead, the ratchet wheel will be angularly displaced in the opposite direction and also to the same degree.

It will be seen that a combination torsion spring and compression spring 50 is disposed about each armature. The compression portion 52 of the spring is disposed between the washer 42 and the top surface of the solenoid core. The spring also acts in a torsional manner since one end 54 (FIG. 2) is abutting the free end of the pawl and the opposite end 56 of the spring is positioned against a surface, in this case the face of the ratchet wheel 22. The spring therefore serves two functions. First, the compression part of the spring urges the solenoid armature in an upwardly direction. Secondly, the torsional action of the spring urges the pawl in the direction of the ratchet teeth.

The top leg of the chassis 12 has a pair of downwardly depending tabs 60 that serves a very useful function in cooperation with the free end of the pawl members. In the embodiment illustrated it will be seen that the tabs each have a vertical edge 62 and a horizontal edge 64. In the normal position, when a solenoid is de-energized, an upwardly turned flange 66 on each pawl is urged into abutment with the vertical edge 62 of the chassis tab. This action is provided by the torsional component of the spring. At the same time the horizontal edge 64 of each tab is in abutment with the horizontal body portion 68 of the pawl due to the urging provided by the compression action of the spring. Thus it will be seen that the coshould be noted that the resilient member need not be ball-shaped and other shapes will function providing the material is elastomeric. Other suitable forms may be cubes, cylinders and short sections of rods. The resilient member allows the armature to bounce, thereby contributing to the self-pulsing or self-stepping when power is applied.

The source of the pulsing action is the 60' cycle/sec. applied voltage. However, 60 cycle power is too fast for the inertia of the system to follow. Therefore, a diode 74 is introduced into the circuit, as shown in FIG. 6, to reduce the power and eliminate /2 the cycle sine wave. This provides 60 cycles/sec. of unidirectional power rather than 120 cycles/sec. of bidirectional power. In FIG. 6 the solenoid coils 34 are schematically shown and designated 34a and 3417. When voltage is applied across the terminals of coil 34a clockwise rotation is imparted and when voltage is applied across the terminals of coil 34b, counterclockwise rotation is imparted. It should be apparent that the reduction of power from 120 cycles per second of bi-directional power to 60* cycles per second of uni-directional power not only makes a structure that is easier to build but functions exceptionally well with the elastomeric member 70, so that the self-pulsing or self-stepping feature of the invention may be accomplished with greatly reduced power.

It will be appreciated that the number of steps that may be imparted to the potentiometer shaft is a function of the number of teeth on the ratchet wheel as well as the length of stroke of the armature. More or less teeth on the ratchet wheel will permit more or less steps for the potentiometer shaft. While it has not been specifically illustrated, it is also within the scope of this invention to make the position of the horizontal edge of the chassis tab variable so that the stroke of the armature may be carefully controlled. At the same time the position of the vertical edge of the chassis tabs could also be made adjustable so that the upper end of its stroke, the edge of the pawl that engages the tooth is always positioned closely to the next tooth.

From the foregoing it will be clear that the construction of the apparatus shown in the drawing permits both manual and remote movement of a potentiometer shaft. The remote actuation is accomplished in a step-wise manner in either of the two opposite directions. Within the limits of the steps fixed within the potentiometer, a number of step-wise movements of the potentiometer shaft is permitted. When the solenoids are de-energized, the pawls are close to but out of contact with the ratchet wheel so that the manual mode may be used by rotating an external knob (not shown).

What is claimed is:

1. Apparatus for indexing a potentiometer shaft of a potentiometer in two angularly opposite directions and in equal, stepwise increments, said apparatus comprising a chassis supporting said potentiometer, a ratchet member secured to the potentiometer shaft for rotation therewith, first and second movable pawl members positioned in a non-operating condition in proximity to the periphery of said ratchet member, a spring coacting with each pawl member to selectively move each pawl to said non-operating condition thereof, said pawl members being on opposite sides of the longitudinal axis of the potentiometer shaft, electrically actuated solenoid means constituting a first and second solenoids each having an armature rigidly coupled to each of said pawl members, said solenoids being arranged to displace a selected one of said pawl members, each of said solenoids having an electrically energizable coil, an electrical power circuit including diode means therein being electrically connected to said solenoid coils whereby reduced uni-directional power is transmitted to said coils, a hollow support bobbin for each coil, and an elastomeric resilient member in said support bobbin under the inner end of said armature whereby when the armature moves inwardly when electrical power is applied to said coil said armature makes a bouncing contact with said elastomeric resilient member, and said armature moves axially and said pawl member engages said ratchet member.

2. Apparatus as claimed in claim 1 wherein said elastomeric resilient member is of a medium hardness that provides sufficient bounce to said armature together with sufificient damping.

3. Apparatus as claimed in claim 1 wherein said solenoid coils are connected in series and said diode is connected between said coils whereby when voltage is applied across the terminals of one of said coils clockwise rotation is imparted to said potentiometer shaft, and when voltage is applied across the terminals of the other of said coils counterclockwise rotation is imparted to said potentiometer shaft.

4. Apparatus as claimed in claim 1 wherein said spring is a combination compression and torsion spring adapted to move the adjacent pawl axially and laterally.

5. Apparatus as claimed in claim 1 wherein said elastomeric resilient member is constituted of rubber.

References Cited UNITED STATES PATENTS 1,623,026 3/ 1927 Cabezola 310-23 2,768,314 10/1956 Ruckelshaus 74--128 X 2,829,530 4/1958 Holden 310-23 X 2,851,619 9/1958 Jones 31024 2,963,633 12/ 1960 Bowditch 318122 X 3,024,375 3/ 1962 Tyzack 310-24 DONOVAN F. DUGGAN, Primary Examiner U.S. C1.X.R. 

